20 Shaping, Planing and Slotting Machines.

8/14/2019 20 Shaping, Planing and Slotting Machines.

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Module4

General purposemachine tools

Version 2 ME, IIT Kharagpur


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Lesson20Construction, working

principle andapplications of

shaping,planing and slotting

machines .Version 2 ME, IIT Kharagpur


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Instructional objectivesAt the end of this lesson, the students will be able to;

(i) Demonstrate the configurations and functions of shaping machine,planing machine and slotting machine

(ii) Illustrate the kinematic systems and explain the working principles ofshaping machine, planing machine and slotting machine

(iii) Show and describe the various machining applications of shaping,planing and slotting machines.

(i) Configurations and basic functions of Shaping machines Planing machines Slotting machines

Shaping machine

A photographic view of general configuration of shaping machine is shown inFig. 4.4.1. The main functions of shaping machines are to produce flatsurfaces in different planes. Fig. 4.4.2 shows the basic principle of generationof flat surface by shaping machine. The cutting motion provided by the linearforward motion of the reciprocating tool and the intermittent feed motionprovided by the slow transverse motion of the job along with the bed result inproducing a flat surface by gradual removal of excess material layer by layerin the form of chips. The vertical infeed is given either by descending the toolholder or raising the bed or both. Straight grooves of various curved sectionsare also made in shaping machines by using specific form tools. The singlepoint straight or form tool is clamped in the vertical slide which is mounted atthe front face of the reciprocating ram whereas the workpiece is directly or

indirectly through a vice is mounted on the bed.



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Planing machine

The photographic view in Fig. 4.4.3 typically shows the general configurationof planing machine. Like shaping machines, planing machines are alsobasically used for producing flat surfaces in different planes. However, themajor differences between planing machines from shaping machines are :

o Though in principle both shaping and planing machines produce flatsurface in the same way by the combined actions of the Generatrixand Directrix but in planing machine, instead of the tool, theworkpiece reciprocates giving the fast cutting motion and instead ofthe job, the tool(s) is given the slow feed motion(s).

o Compared to shaping machines, planing machines are much largerand more rugged and generally used for large jobs with longerstroke length and heavy cuts. In planing machine, the workpiece ismounted on the reciprocating table and the tool is mounted on thehorizontal rail which, again, can move vertically up and down alongthe vertical rails.

o Planing machines are more productive (than shaping machines) forlonger and faster stroke, heavy cuts (high feed and depth of cut)possible and simultaneous use of a number of tools.

As in shaping machines, in planing machines also; The length and position of stroke can be adjusted Only single point tools are used The quick return persists Form tools are often used for machining grooves of curved section Both shaping and planing machines can also produce large curved

surfaces by using suitable attachments.

Cutting tool in action

Fig. 4.4.3 Photographic view of a planing machine



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Slotting machine

Slotting machines can simply be considered as vertical shaping machinewhere the single point (straight or formed) reciprocates vertically (but withoutquick return effect) and the workpiece, being mounted on the table, is givenslow longitudinal and / or rotary feed as can be seen in Fig. 4.4.4. In thismachine also the length and position of stroke can be adjusted. Only light cutsare taken due to lack of rigidity of the tool holding ram for cantilever mode ofaction. Unlike shaping and planing machines, slotting machines are generallyused to machine internal surfaces (flat, formed grooves and cylindrical).Shaping machines and slotting machines, for their low productivity, aregenerally used, instead of general production, for piece production requiredfor repair and maintenance. Like shaping and slotting machines, planingmachines, as such are also becoming obsolete and getting replaced by plano-millers where instead of single point tools a large number of large size andhigh speed milling cutters are used.

Cutting tool in action

Fig. 4.4.4 Photographic view of a slotting machine



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(ii) Kinematic system and working principles of Shaping machine Planing machine Slotting machine

Shaping machine

The usual kinematic system provided in shaping machine for transmittingpower and motion from the motor to the tool and job at desired speeds andfeeds is schematically shown in Fig. 4.4.5.

Oscillating lever

leadscrew

crank

column

Bull gear

ram

bed

base

Fig. 4.4.5 Kinematic diagram of a shaping machine.

The central large bull gear receives its rotation from the motor through thebelt-pulley, clutch, speed gear box and then the pinion. The rotation of the



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crank causes oscillation of the link and thereby reciprocation of the ram andhence the tool in straight path. Cutting velocity which needs to be varieddepending upon the tool-work materials, depends upon

The stroke length, S mm Number of strokes per min., N s and The Quick return ratio, QRR (ratio of the durations of the forward

stroke and the return stroke)

As, 111000

s C

sxN V

QRR = +

/minm (4.5.1)

To reduce idle time, return stroke is made faster and hence QRR > 1.0 (4.5.2)

Since 22

L s QRR

L s

+=

(4.5.3)

where, L = length (fixed) of the oscillating leverand s = stroke length

The benefit of quick return decreases when S becomes less.The changes in length of stroke and position of the stroke required fordifferent machining are accomplished respectively by

Adjusting the crank length by rotating the bevel gear mountedcoaxially with the bull gear

Shifting the nut by rotating the leadscrew as shown in Fig. 4.4.5.The value of N s is varied by operating the speed gear box.The main (horizontal) feed motion of the work table is provided at differentrate by using the ratchet paul systen as shown in Fig. 4.4.5. The verticalfeed or change in height of the tool tip from the bed can be obtained either bylowering the tool or raising the bed by rotating the respective wheel asindicated in Fig. 4.4.5.

Planing machine

The simple kinematic system of the planing machine enables transmissionand transformation of rotation of the main motor into reciprocating motion ofthe large work table and the slow transverse feed motions (horizontal andvertical) of the tools. The reciprocation of the table, which imparts cuttingmotion to the job, is attained by rack-pinion mechanism. The rack is fitted withthe table at its bottom surface and the pinion is fitted on the output shaft of thespeed gear box which not only enables change in the number of stroke per

minute but also quick return of the table.The blocks holding the cutting tools are moved horizontally along the rail byscrew-nut system and the rail is again moved up and down by another screw-nut pair as indicated in Fig. 4.4.3.

Slotting machine

The schematic view of slotting machine is typically shown in Fig. 4.4.6The vertical slide holding the cutting tool is reciprocated by a crank andconnecting rod mechanism, so here quick return effect is absent. The job, tobe machined, is mounted directly or in a vice on the work table. Like shaping

machine, in slotting machine also the fast cutting motion is imparted to thetool and the feed motions to the job. In slotting machine, in addition to the



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longitudinal and cross feeds, a rotary feed motion is also provided in the worktable.The intermittent rotation of the feed rod is derived from the driving shaft withthe help of a four bar linkage as shown in the kinematic diagram.It is also indicated in Fig. 4.4.6 how the intermittent rotation of the feed rod is

transmitted to the leadsrews for the two linear feeds and to the worm wormwheel for rotating the work table. The working speed, i.e., number of strokesper minute, N s may be changed, if necessary by changing the belt-pulley ratioor using an additional speed gear box, whereas, the feed values arechanged mainly by changing the amount of angular rotation of the feed rodper stroke of the tool. This is done by adjusting the amount of angle ofoscillation of the paul as shown in Fig. 4.4.6. The directions of the feeds arereversed simply by rotating the tapered paul by 180 o as done in shapingmachines.

Vertical ram

Driving shaft

Rotating table

Feed rod

Fig. 4.4.6 Kinematic system of a slotting machine.



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(iii) Various applications of Shaping machine Planing machines Slotting machines

Shaping machines

It is already mentioned that shaping machines are neither productive norversatile.However, its limited applications include :

Machining flat surfaces in different planes. Fig. 4.4.7 shows how flatsurfaces are produced in shaping machines by single point cutting

tools in (a) horizontal, (b) vertical and (c) inclined planes.

(a) horizontal surface (b) vertical surface

FMCM FM

CM

FM CMFM

CM

(c) inclined surfaces (dovetail slides and guides)

Fig. 4.4.7 Machining of flat surfaces in shaping machines

Making features like slots, steps etc. which are also bounded by flatsurfaces. Fig. 4.4.8 visualises the methods of machining (a) slot, (b)pocket (c) T-slot and (d) Vee-block in shaping machine by singlepoint tools.

Forming grooves bounded by short width curved surfaces by usingsingle point but form tools. Fig. 4.4.9 typically shows how (a) oilgrooves and (b) straight tooth of spur gears can be made in shapingmachine

Some other machining applications of shaping machines are cutting

external keyway and splines, smooth slitting or parting, cutting teeth



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of rack for repair etc. using simple or form type single point cuttingtools.Some unusual work can also be done, if needed, by developing andusing special attachments.

(a) slotting (b) pocketing (c) T-slot cutting

(d) Vee-block

Fig. 4.4.8 Machining (a) slot, (b) pocket (c) T-slot and (d) Vee block in shaping machine



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(a) grooving (b) straight tooth cutting for spur gears

Fig. 4.4.9 Making grooves and gear teeth cutting in shaping machine by form tools .

However, due to very low productivity, less versatility and poor processcapability, shaping machines are not employed for lot and even batchproduction. Such low cost primitive machine tools may be reasonably usedonly for little or few machining work on one or few pieces required for repairand maintenance work in small machine shops.

Planing machines

The basic principles of machining by relative tool-work motions are quitesimilar in shaping machine and planing machine. The fast straight path cuttingmotion is provided by reciprocation of the tool or job and the slow, intermittenttransverse feed motions are imparted to the job or tool. In respect ofmachining applications also these two machine tools are very close. All theoperations done in shaping machine can be done in planing machine. Butlarge size and stroke length and higher rigidity enable the planing machinesdo more heavy duty work on large jobs and their long surfaces. Simultaneoususe of number of tools further enhances the production capacity of planingmachines.The usual and possible machining applications of planing machines are

The common machining work shown in Fig. 4.4.7, Fig. 4.4.8 andFig. 4.4.9 which are also done in shaping machines

Machining the salient features like the principal surfaces andguideways of beds and tables of various machines like lathes,milling machines, grinding machines and planing machines itself,broaching machines etc. are the common applications of planingmachine as indicated in Fig. 4.4.10 where the several parallelsurfaces of typical machine bed and guideway are surfaced by anumber of single point HSS or carbide tools. Besides that the longparallel T-slots, Vee and inverted Vee type guideways are also

machined in planing machines.



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(a) through rectangular hole (b) hexagonal socket

Fig. 4.4.11 Typical machining application of slotting machine.

However, it has to be borne in mind that productivity and process capability ofslotting machines are very poor and hence used mostly for piece productionrequired by maintenance and repair in small industries. Scope of use ofslotting machine for production has been further reduced by more and regularuse of broaching machines.



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Exercise

Identify the correct answer from the given four options.

1. Reciprocation of the cutting tool in shaping machines is accomplished bya. Rack pinion mechanismb. Crank and connecting rod mechanismc. Cam and cam follower mechanismd. Oscillating lever mechanism

2. Internal keyway in gears can be cut ina. Shaping machineb. Planing machinec. Slotting machined. None of the above

3. The job reciprocates in

a. Shaping machineb. Planing machinec. slotting machined. All of the above

4. The T-slots in the table of planing machines are cut ina. Shaping machineb. Planing machinec. Slotting machined. None of the above

5. Flat surface can be produced ina. Shaping machine only

b. Planing machine onlyc. Slotting machine onlyd. All of the above

6. Large number of cutting tools can be simultaneously used ina. Shaping machineb. Planing machinec. Slotting machined. None of the above



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7. Heavy cuts can be given during machining ina. Shaping machineb. Planing machinec. Slotting machined. None of the above

8. Slotting machines are used to cut internal gear teeth fora. Batch productionb. Lot productionc. Mass productiond. None of the above

9. The work-table can rotate ina. Shaping machineb. Planing machinec. Slotting machined. None of the above

10. Length of the stroke can be varied ina. Shaping machineb. Planing machinec. Slotting machined. All of the above

Answers

Q.No Answers

1 d2 c3 b4 b5 d6 b7 b8 a9 c

10 b


20 Shaping, Planing and Slotting Machines.

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